The pharmacologic management of acute spinal cord injury in humans remains equivocal despite decades of animal clinical investigation. The National Acute Spinal Cord Injury Study (NASCIS) was established in 1977 to evaluate new treatment modalities using a multi-center randomized clinical trial (RCT) methodology. The first RCT (NASCIS I) was successfully completed in 1983. Recent animal data suggests that high doses of Methylprednisolone (30 mg/k and Naloxone (5 mg/k) may be efficacious in improving neurological recovery after acute spinal cord injury. It is proposed to compare these drugs against placebo in a double blind RCT at twelve medical centers. The study protocols will be modified after existing ones already developed by the study group. Eligible spinal cord injury patients will be randomized to one of three treatment arms within 18 hours fo injury. Standardized neurologic exams will be given on admission, 24, 48 and 72 hours, and six weeks, six months and one year after injury. Improvement in motor function, pinprick, light touch and deep pressure sensation are the major study outcome measures. Morbidity and mortality, especially as they relate to drug treatment, will be monitored throughout the trial and studied in detail. A total of 480 patients will be randomized. Potential confounding and effect modifying factors will be examined and controlled using log linear models and logistic regression analyses. The National Acute Spinal Cord Injury Study is one of the most detailed, standardized and complete data sets of the management of acute spinal cord injury available. It will also be used, therefore, to test hypotheses concerning the potential advantages of surgical and other management procedures in improving neurological outcomes.